According to the New York Times, scientists are now monitoring 38 HIV positive patients, 32 of whom have been given bone-marrow transplants from a donor with the CCR5 gene mutation. He was treated with anti-retroviral drugs until about 18 months ago.
The scientists are describing the case as a long-term remission publically, while most experts are calling it a cure, the paper reported. "We can't detect anything", said Ravindra Gupta, a professor and HIV biologist who co-led a team of doctors treating the man.
The problems cleared up without intervention, though, and the patient was left with immune cells that lacked the protein used by HIV. About 37 million people worldwide now have HIV, and the AIDS virus has killed about 35 million since taking off in the 1980s.
The vast majority of HIV virus strains use the CCR5 molecule, or receptor, as the port of entry into human cells. Nearly one million people die annually from HIV-related causes.
The patient - a British man who prefers to remain anonymous - was first diagnosed with HIV in 2003. Later that year he was diagnosed with Hodgkin's Lymphoma and needed chemotherapy. This mutation of the CCR5 gene makes the people who carry it resistant to HIV. HIV can mutate from using CCR5 to relying on CXCR4, but in order to do that, it needs to be actively replicating.
Current HIV therapies are really effective, meaning people with the virus can live long and healthy lives. This transient immune response may help kill off the last surviving cells of the host's immune system-possibly specifically those carrying HIV. A variety of "reservoirs" of HIV-infected cells has been identified; all of the significant ones appear to be in immune cells of one type or another. After chemotherapy, he underwent a stem cell transplant in 2016 and subsequently remained on antiretroviral therapy for 16 months.
In the decade between the two successful cases there were other similar operations, but the patients died of cancer before it could be determined if Brown's case was an aberration. He is tested often, and his HIV viral load is undetectable.
"The first is that CCR5-negative cells are resistant to HIV", she said.
But there was something unusual about the person who gave the London patient stem cells. Interestingly, the donor's stem cells had a mutation named CCR5 delta 32.
"Although this is not a viable large-scale strategy for a cure, it does represent a critical moment", said Anton Pozniak, president of the International AIDS Society.
"This tells us that the feasibility, and importantly, the availability of delivering this approach could possibly be achieved by the rapidly accelerating field of gene editing and related gene therapies".
The therapy had an early success with Timothy Ray Brown, a United States man treated in Germany who is 12 years post-transplant and still free of HIV.
Gupta, now at Cambridge University, treated the London patient when he was working at University College London. They also plan to present details in Seattle at the Conference on Retroviruses and Opportunistic Infections, which began Monday. Note: material may have been edited for length and content. In 2007, he received a rare form of bone marrow transplant involving haematopoietic stem cells to treat his leukaemia.